1. Field of the Invention
The invention relates to a pressure vessel, more particularly to a hydro-pneumatic pressure vessel with a protecting unit.
2. Description of the Related Art
Hydro-pneumatic pressure vessels are at present widely used in industrial and residential pump piping system, for example, for stabilizing water pressure and absorbing water hammers.
The basic configuration of a hydro-pneumatic pressure vessel includes a first vessel, a second vessel coupled to the first vessel and an elastic diaphragm that is made of rubber and that is disposed for dividing an inner space in the first and second vessels into a water chamber and an air chamber. A water fitting and an air valve are provided respectively on the first and second vessels to communicate fluidly and respectively the water chamber and the air chamber. Hydro-pneumatic pressure vessels with such configuration are disclosed in U.S. Pat. Nos. 4,192,350, 4,351,363, 4,723,577, 4,784,181, etc. In the above, the diaphragm illustrated in U.S. Pat. No. 4,784,181 is a bladder-type diaphragm.
When the water pressure drops suddenly, the diaphragm may be pushed toward the water fitting by the pressure inside the air chamber. Consequently, a portion of the diaphragm may be damaged due to being squeezed into a water ports of the water fitting. To alleviate the damage, some solutions are disclosed in the present art. For example, in a first solution, as disclosed in U.S. Pat. Nos. 4,192,350 and 4,351,363, a metal block is embedded in the portion of the diaphragm that would be drawn to the water port during the deformation of the diaphragm. In a second solution, as disclosed in U.S. Pat. No. 4,723,577, the thickness of the portion of the diaphragm is increased. In a third solution, as shown in FIG. 1, another conventional pressure vessel has the water fitting 101 welded to a plate 105 formed with a plurality of small holes 102. The water chamber 103 communicates with the water fitting 101 via the small holes 102, while the diaphragm 104 can be blocked by the plate 105.
The above-mentioned solutions have a favorable effect in a hydro-pneumatic pressure vessel having an air pressure in the air chamber under 16 kg/cm2. However, when the hydro-pneumatic pressure vessel is used in skyscrapers, the air pressure must be enhanced to 25 kg/cm2 or higher for the practical necessity. As a result, all the above mentioned solutions can hardly attain the effect as in a lower pressure application. In the first solution, the connection between the rigid metal block and the elastic diaphragm may be affected under such high pressure. In the second solution, the portion of the diaphragm may be damaged. In the third solution, the diaphragm 104 may be squeezed into the small holes 102.